According to the group from the Fraunhofer Institute for Surface Engineering the secret lies in the printing process, where the individual layers are treated with a cold plasma in order to improve the bonding of bone-forming cells.
Whereas conventional surface treatments using low-pressure or atmospheric pressure techniques have a limited penetration into the interior of bone implants, the new method makes it possible to apply a cell-growth-promoting coating to the interior of the implants.
The team’s technique works by blowing a cold jet of plasma containing reactive groups directly onto the printed layers. The amino groups bond with the surface and ensure that bone cells find a convenient substrate to which they readily adhere.
A unique feature of the technique is that the 3D printing and coating processes go hand in hand and are combined in one device. Because no chemical pre-treatment with solvents is required for the coating, it is not only cost-effective, but environmentally friendly also. The scaffold around which the implant is built is made from a special copolymer that is modelled on the natural bone.
The 3D printing technique permits very individual, precisely fitting design and stability. “Our goal is for the bone cells to grow into the synthetic structure as quickly as possible and finally replacing the implant which is broken down gradually by the body’s own enzymes,” explained Dr. Jochen Borris, who heads up the Life Science and Ecology business unit at Fraunhofer IST.
The mechanical stability of the implant can be controlled not only via the density of the printed scaffold structure, but also via special fillers that are added to the copolymer: the higher the filler concentration, the greater the stability. Moreover, active drug ingredients such as antibiotics can be incorporated in the filler to reduce the risk of infection.
The project team is now working on simplifying the process and looking for industrial partners who may be able to help bring the technique to market.
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